For rotating devices, such as a turbocharger, a rotating electrical machine, and a power generator turbine, it is necessary to enhance the precisions of respective components of the rotating devices to reduce vibration caused by the rotation of a rotator. In addition to such enhancement, imbalance of the assembled rotating devices is corrected (correction of imbalance). According to the imbalance correction method proposed in Patent Document 1 (Japanese Laid-Open Patent Publication No. 2003-302305) and to a turbocharger assembly, it is attempted to accurately correct the imbalance through two corrections. More specifically, the imbalance correction method disclosed in Patent Document 1 (Japanese Laid-Open Patent Publication No. 2003-302305) performs measurement twice and correction twice on a turbocharger assembly. In the first measurement, an initial imbalance is measured, and in the first correction, such an initial imbalance is eliminated. Next, the second measurement is performed on the turbocharger assembly having undergone the first correction, thereby measuring the remaining imbalance. The measured remaining imbalance is not directly corrected, but is corrected at first based on the ratio of the initial imbalance measured through the first measurement to the corrected level actually performed in the first correction. Next, the second correction is performed so as to correct the remaining imbalance having undergone the correction.
The balance tester proposed in Patent Document 2 (Japanese Laid-Open Patent Publication No. 2005-308538) detects imbalance only at a certain rotation speed (a rotation speed at the time of actual operation in most cases) of a rotator, and the imbalance is corrected based on the detection result or the imbalance is corrected while assuming that the rotator is a rigid body, thereby addressing the technical disadvantage of an imbalance correction method. More specifically, the balance tester of Patent Document 2 (Japanese Laid-Open Patent Publication No. 2005-308538) includes a rotor holding device having a holder member that holds a rotor (rotator) and driven at an arbitrary rotating speed, a rotation speed detector that detects a rotation speed of the rotor, and a vibration detector that detects an imbalance vibration of the rotor at one or multiple locations in the axial direction of the rotor. The rotating speed detector and the vibration detector measure the imbalance vibration of the rotor for each arbitrary rotation speed set in advance from the slowest rotation speed to the fastest rotation speed. The balance tester calculates a correction weight to be added or subtracted at certain location (corrected face) of the rotor in the axial direction set in advance based on the measured result. The imbalance tester of Patent Document 2 (Japanese Laid-Open Patent Publication No. 2005-308538) includes a control device, which predicts a remaining vibration at each rotation speed when it is presumed that the correction weight is added to or subtracted from the corrected face, and displays the weight level of the correction weight to be attached to the corrected face and the phase angle. The tester measures the remaining vibration with the correction weight corresponding to the weight level displayed by the control device being actually attached to the corrected face, and repeats those successive processes until the remaining vibration becomes smaller than a managing value. The correction weight is calculated through the lowest square technique.